Arrangements that can be used at ventilation arrangements in order to hold and control a channel through which air and thus hazardous substances and gases may be withdrawn are known. The term “ventilation arrangement” is here used to denote all parts and fittings that constitute the ventilation arrangement, and this arrangement also comprises, among other parts, a unit that can create negative pressure, a force of suction, that acts on the air in the flexible channel and various parts and constructions that lead, distribute, retain, guide, regulate and in other ways ensure that the ventilation arrangement works in the manner desired. These arrangements are relatively heavy constructions manufactured from steel. They are heavy to transport and assemble, they become difficult to manoeuvre, and thus they require a lot of space in use.